With the ever-growing demand for higher performance at lower cost, the feature dimensions of integrated circuits continue to shrink. As a consequence, there is an increase in the interconnect (RC) delay and signal degradation at the back-end-of-line (BEOL) wiring of semiconductor chips. In order to reduce the capacitance, effort has been focused on development of new low dielectric constant insulating materials having a dielectric constant lower than silicon dioxide, which is a current insulating material. Due to the low dielectric constant of air (k˜1), thin films containing nanometer-sized pores have been recognized as the only viable approach for meeting the goal of dielectric extendibility (that is, the same material composition, varying only in dielectric constant, k) for advanced semiconductor devices. Ideally the k value of a layer decreases in proportion to the fraction of air introduced in the layer. Much effort has been devoted to the generation and characterization of various porous materials.
Efforts to integrate porous dielectrics into chip structures continue. Current BEOL integration schemes require multiple films for pattern generation and protection of the dielectric materials. Patterning spin-on dielectrics involves patterning photoresists coated on dielectrics and subsequent etching and removal of photo-resists. Generally BEOL processing constitutes about 75% of total wafer process cost. There is a continuing desire to simplify BEOL processing and improve performance. However, designing these materials with a controlled porous structure combined with patterning ability is not trivial. A simple, more effective route to patterned, high areal density arrays (e.g., nanoporous thin films) would be highly desirable. Recently, methods for forming a patterned mesoporous material have been described (U.S. Patent Application Publication, US2002/0127498 A1 to Doshi et al.; Clark, Jr. et al., Chem. Mater. 2000, 12, 3879), but the porous films in these studies are limited to hydrophilic silica and show variable morphologies, since the porous structure was generated from dynamically templated organic/inorganic hybrid films using surfactants.